In a semiconductor rectifying device that rectifies an input current to output the rectified current, there are a PiN diode having a pn junction and a Schottky barrier diode (SBD) having a carrier potential barrier of a difference in work function between a semiconductor layer and metal. In the Schottky barrier diode, there is a JBS (Junction Barrier Schottky barrier diode) in which an impurity region (for example, p type) having a conductive type different from that of the semiconductor layer (for example, n type) is disposed in a surface of the semiconductor layer in order to relax an electric field applied to an interface between the semiconductor layer and the metal. There is also an MPS (Merged PiN-diode Schottky-diode), in which the contact between the impurity region (for example, p type) and the metal of the JBS is set to or brought close to ohmic connection, and a minority carrier is injected to decrease a resistance by conductivity modulation when a voltage exceeding a built-in potential (Vbi) between the impurity region and the semiconductor layer is applied.
On the other hand, a wide bandgap semiconductor such as silicon carbide (hereinafter also referred to as SiC) is expected as a next-generation power semiconductor device. The wide bandgap semiconductor has a wide bandgap, high breakdown field strength, and high thermal conductivity compared with Si. A low-loss power semiconductor device that can be operated at high temperature can be implemented using the characteristics of the wide bandgap semiconductor.
In the MPS, generally the impurity region is formed by ion implantation of an impurity. However, ion implantation damage exists in the high-concentration impurity region formed by the ion implantation. Therefore, unfortunately an on-voltage of the semiconductor rectifying device is increased, and hole injection is delayed to increase a switching loss when an off-state is switched to an on-state.